I'm creating a small gameworld for school in Unity. It needs a city n' stuff, so we can use the worlds in VR. The school has computers with an older version of Unity, and respectively, models from the Asset Store that are compatible with that version and below. Contrastly, my computer has the latest version of Unity and all the Asset Store assets available to me.
Question is, if I use newer assets in my world, then import the project to an older version of Unity, will there be and major issues with the assets? Or will those assets just simply refuse to port?
It all depends on the package. I would say you're going in the more difficult direction, as Unity does pretty well with being able to integrate deprecated packages into newer versions of Unity, but not as well with bringing newer assets into older versions of Unity.
I would suspect things like simple models would be fine, but if you try anything that dives more deeply into scripting/animation/lighting (I know I've had trouble with Text Mesh Pro going in both directions), you might run into some difficulties.
I would download the matching version of Unity and work within that to be on the safe side and avoid integration issues entirely.